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Linux 2.6 - man page for gmtime (linux section 3posix)

GMTIME(P)			    POSIX Programmer's Manual				GMTIME(P)

NAME
       gmtime, gmtime_r - convert a time value to a broken-down UTC time

SYNOPSIS
       #include <time.h>

       struct tm *gmtime(const time_t *timer);

       struct tm *gmtime_r(const time_t *restrict timer,
	      struct tm *restrict result);

DESCRIPTION
       For  gmtime():	 The  functionality  described on this reference page is aligned with the
       ISO C standard. Any conflict between the requirements described here and the  ISO C  stan-
       dard is unintentional. This volume of IEEE Std 1003.1-2001 defers to the ISO C standard.

       The  gmtime()  function	shall  convert	the time in seconds since the Epoch pointed to by
       timer into a broken-down time, expressed as Coordinated Universal Time (UTC).

       The relationship between a time in seconds since the Epoch used as an argument to gmtime()
       and the tm structure (defined in the <time.h> header) is that the result shall be as spec-
       ified in the expression given in the definition of seconds since the Epoch (see	the  Base
       Definitions  volume of IEEE Std 1003.1-2001, Section 4.14, Seconds Since the Epoch), where
       the names in the structure and in the expression correspond.

       The same relationship shall apply for gmtime_r().

       The gmtime() function need not be reentrant. A function that is not required to	be  reen-
       trant is not required to be thread-safe.

       The  asctime(), ctime(), gmtime(), and localtime() functions shall return values in one of
       two static objects: a broken-down time structure and an array of type char.  Execution  of
       any  of the functions may overwrite the information returned in either of these objects by
       any of the other functions.

       The gmtime_r() function shall convert the time in seconds since the Epoch  pointed  to  by
       timer  into  a broken-down time expressed as Coordinated Universal Time (UTC). The broken-
       down time is stored in the structure referred to by result. The gmtime_r() function  shall
       also return the address of the same structure.

RETURN VALUE
       Upon  successful  completion, the gmtime() function shall return a pointer to a struct tm.
       If an error is detected, gmtime() shall return a null pointer	and set errno to indicate
       the error.

       Upon  successful  completion, gmtime_r() shall return the address of the structure pointed
       to by the argument result.  If an error	is  detected,  gmtime_r()  shall  return  a  null
       pointer.

ERRORS
       The gmtime() function shall fail if:

       EOVERFLOW
	      The result cannot be represented.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       The  gmtime_r()	function  is  thread-safe  and	returns  values in a user-supplied buffer
       instead of possibly using a static data area that may be overwritten by each call.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       asctime() , clock() , ctime() , difftime() , localtime() , mktime() , strftime()  ,  strp-
       time() , time() , utime() , the Base Definitions volume of IEEE Std 1003.1-2001, <time.h>

COPYRIGHT
       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  Portable	Operating  System
       Interface  (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
       the Institute of Electrical and Electronics Engineers, Inc and  The  Open  Group.  In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					GMTIME(P)


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